1. Field of the Invention
This invention relates generally to friction clutch and braking devices and more particularly relates to unique devices of this type wherein specially tailored carbon and graphite composite materials are used as friction facing materials.
2. Description of the Prior Art
In clutches, brakes, automatic transmissions, limited slip differentials, hoists and similar friction power transmission and energy absorption devices, there is generally provided one or more sets of cooperating members, one of which is typically a driving or acting member and the other of which is typically a driven or acted upon member. Generally at least one of the members has a friction material surface adapted to be moved into and out of frictional engagement with an opposing surface of the cooperating member.
In liquid cooled friction power transmission-energy absorption devices, one of the cooperating surfaces is typically of solid metal and mechanical means are provided to accomplish the selective engagement and disengagement with this surface of a friction material typically provided in the form of a facing which is affixed to the second cooperating member. Typically both the acting and acted upon members move in a liquid, generally some type of cooling oil, and frequently the oil is force circulated about and between the engaging surfaces of the members so as to continuously cool them.
Heretofore, the so-called friction material or friction facing used in wet power transmission-energy absorption devices has been predominantly asbestos or composite materials containing asbestos. Under heavy load, high temperature applications these prior art friction facing materials have exhibited various deficiencies. Frequently, for example, they decompose and char due to heating even when they are arranged to run in a cooling medium. As the material degrades in use it tends to chatter, glaze and, under severe conditions, will fracture placing the entire assembly in jeopardy of serious damage.
For certain critical friction power transmission-energy absorption applications, the use of carbon and graphite materials has been suggested. For example a superior composite material for use in aircraft brakes has been developed by the present inventor. This material is described in U.S. Pat. No. 3,991,248. The herein named inventor is also aware of a proposed graphite friction facing material described in British Pat. No. 1,101,471 which issued to the Abex Corporation. This latter material, however, unlike the material described herein, in the preferred form, is constructed of a powdered carbon or graphite bonded together by a resin binder.
As will be discussed in detail in the paragraphs which follow, applicant has developed a unique friction power transmission-energy absorbtion assembly and a carbon composite friction facing material for use therein, which effectively overcomes the deficiencies of prior art systems and exhibits particularly superior characteristics in wet, or liquid cooled, applications.
In accordance with the novel method of the present invention, the carbon composite friction facing material can be specifically tailored for widely diverse applications and operating environments. Through precise control of the densification of the starting substrate, the density, porosity and friction characteristics of the friction facing materials of the invention can be optimized to accommodate numerous operating requirements.